The present invention relates in general to regulated power supplies, and more particularly to a circuit for charging a battery or bank of batteries under predetermined voltage and current requirements.
It is known in the art to charge a battery by applying to it pulsating direct current provided by a silicon controlled rectifier full wave bridge running directly from an alternating current power line. The duration or pulse width of each direct current pulse is regulated so as not to apply too much voltage or too much current to the battery undergoing charging. The regulation of the pulse width is accomplished by varying the firing angles of the silicon controlled rectifiers forming a part of the full wave bridge.
It is also known to use a unijunction transistor oscillator of the relaxation type for providing triggering pulses to the gates of the silicon controlled rectifiers at the appropriate times to establish the desired pulse widths for the direct current pulses being applied to the battery undergoing charging.
The pulse widths are varied by the oscillator in response to the sensing and continuous monitoring, in a closed loop feedback manner, of the output voltage applied across the battery and the output current provided to it by the charging circuit. A pair of operational amplfiers, one for output current regulation and one for output voltage regulation, in the output voltage and current monitoring feedback loops, regulates the operation of the oscillator, and thus the firing angles of the silicon controlled rectifiers in the bridge.
The use of operational amplifiers in the above-noted manner has inherent disadvantages in terms of desired response time, gain and temperature-stability.